For stationary or traction combustion-engines, generally a gaseous fuel is supplied at about atmospheric pressure and mixed with air in a gas-air mixer. This low pressure is required to prevent that gas from streaming outside the mixer before starting or when the engine is standing still, which causes a danger of explosion. Such gas-air mixtures are led directly after mixing to the combustion chambers of the combustion engine. As a fuel, gaseous fuels or fluidic fuels are applied.
For the combustion process, the gas-air mixing ration is of prime importance and is called stoichiometric, as just enough air is present for the complete combustion of the present gas volume. Generally excess air is applied or inert (exhaust) gas is added to the combustion mixture to reduce the undesired oxygen-nitrogen combinations.
As a gaseous fuel, generally natural gas, propane or LPG is used. The stoichiometric air-gas ratio is defined as lambda 1.0 and is one of the most important variables for the combustion process, as are the composition and temperature of the exhaust gases. Generally the combustion in gas engines is performed with a lambda value between 1.0 (rich mixture) and 1.6 (lean mixture), whereby a complete combustion of the mixture in the combustion engine is possible.
For lean mixtures a higher compression ratio is employed, without causing detonation, as compared to rich mixtures. The sucking of gas-air mixtures according to the Dutch Patent No. 7605655 is effected by the vacuum pressure of the engine. The sucked air is accelerated in a venturi-tube, by which an underpressure is created for the sucking of the gas in the narrowest section of the annular venturi-tube. The gas volume can be controlled by choking the gas inlet opening by means of a complicated system of membranes and springs, which are activated by the engine vacuum pressure.
However, it appears that harmful non-homogeneity of the mixture remains due to high air speeds in the venturi and consequent short residence-times in the mixer and due to the one-sided gas supply in the throat of the venturi. The drawback of the non-homogenous mixture is overcome by our invention, due to whirling between the created rotational air stream and line air gas stream.
According to the U.S. Pat. No. 2,565,907 the suction of a secondary stream takes place by the expansion in a tangential direction of a primary stream. At the same time, also a strong rotation is developed, which transports the secondary fluid via an annular opening to the place of higher pressure than the suction pressure of the secondary medium itself.
The drawback of this compressive action is that compressed air is required for the expansion process and to overcome the relatively high resistance in the annular opening.
Besides, the nozzles are fixed and convergent for the expansion of the prime medium and also there is the danger of streaming of prime medium in the outlet of the secondary medium when insufficient discharge of the mixture occurs.